I'm sure every owner of a 91 has wrestled with locked rollers when reassembling the rifle. I'm not sure who designed the system, but depressing the bolt retaining arm is a royal pain in the tail. I found an old set of amphenol pliers that take the pain out it all. You can do the same with a channel lock plier after padding the jaws. Tygon tubing works well as a padding material. Since using the pliers I have eliminated the grunting, swearing and dread involved in reassembling the 91's bolt assembly. Maybe someone out there has never found the bolt retaining arm spring to be a challenge, but it was for me. Not so with the use of a simple tool and some tubing.